I'm assuming that this sort of thing should be done in photoshop and not illustrator, so please correct me if you feel otherwise. I'm trying to create circles with blurred stroke in photoshop like the example shown below:
Ignoring the gradient behind the rings, what is the best way to accomplish this? Currently, I'm using the Ellipse Tool with a Fill Opacity of 0% and Stroke (size: 10, opacity: 30%, blend mode: Soft Light). This does not produce the desired results:
Any ideas what I'm doing wrong? Is there a different way to feathering the stroke instead of blurring it?
If you'd like everything to remain editable and scalable at a later date, your best option is to use a shape layer with some mask feathering applied.
That way, you can change the colour, add a gradient or do whatever you like to the circle layer(s), even scale them up or down with no negative side effects.
Note that there's a few ways you can make the circles: You could draw a single circle and use a vector stroke (CS6 only and required to get a blurry edge), or you could draw two shapes and use Subtract Front Shape on the smaller/frontmost one. The later option lets you apply another stroke to the edge (or you could use layer styles).
Let me propose an additional method that may interest you.
First create your arcs as a vector path (in the Paths panel):
Then create a new raster layer and use Stroke Path...:
The current Brush settings will be used (assuming you select Brush) so make sure it has low Hardness and moderate Flow to get a nice soft edge.
If you keep the vector path you can always easily regenerate your blurred strokes.